Dual plate check valves are known which provide substantially one-way fluid flow through a fluid system. A dual plate check valve typically comprises an anchoring base upon which two D-shaped valve plates, sometimes referred to as wings, flaps, or wafers, are pivotally mounted. In use, the check valve is diametrically installed into a tube, or inside an annular housing fitted into a tube. Each valve plate pivots between an open position in which it substantially parallels the desired direction of fluid flow through the system, thereby allowing fluid to flow past the valve through an aperture formed between the base and the tube or annular housing, and a closed position in which it blocks fluid flow in the undesired direction by closing off the aperture.
The valve plates of the check valve are normally pivoted to the open position in response to fluid pressure from fluid flow in the desired direction through the system. For the check valve to prevent fluid flow in the undesired direction, the valve plates must pivot to the closed position in response to either cessation of fluid pressure from the desired direction or commencement of fluid pressure from the undesired direction.
In some dual plate check valves, mechanical means such as springs are used to bias the D-shaped plates into the closed position. For example, U.S. Pat. No. 5,819,790 to Cooper and U.S. Pat. No. 5,711,343 to Beckett describe check valves in which the valve plates are preferably spring-biased to the closed position. However, biasing is undesirable in some applications because additional fluid pressure is necessary to overcome the biasing to open the valve and allow fluid flow in the desired direction. Further, springs can fail due to wear, fatigue, or corrosion, ultimately causing the valve to function improperly or causing damage to the equipment into which the valve is installed.
Accordingly, other check valves have been developed in which the valve plates pivot to the closed position in response to fluid pressure from the undesired direction. In those fluid-actuated check valves, the valve plates typically comprise an elastomer hinge reinforced by metal discs. Because the elastomer hinge is very flexible, fluid pressure on the valve plates from fluid flow in the undesired direction forces the two D-shaped plates into the closed position, while fluid flow in the desired direction forces the valve plates to swing into the open position.
The flexibility of the elastomer hinge can create problems in fluid-actuated check valves when fluid pressure from fluid flow in the undesired direction is sufficiently strong that the valve plates are forced away from the base of the valve. This stretches the elastomer hinge and can cause the metal discs of the valve plates to slide off of the base. In this position, the metal discs can be caught against the side of the base, holding the valve plates in a partially open position. Further, the stretching of the elastomer hinge wears and fatigues it, creating an increasing probability that distortion of the hinge will cause the valve plates to fail to seal correctly against the tube or annular housing in the closed position. Repeated stretching of the elastomer hinge can ultimately lead to distortion or tears in the elastomer hinge, which may allow seepage of fluid past the valve or cause complete failure of the valve.
Another difficulty encountered in fluid-actuated dual plate check valves occurs when fluid pressure from fluid flow in the undesired direction pushes both valve plates to the same side of the base, closing off only one of the apertures. To address this problem, it is known to install a stop pin diametrically into the tube or annular housing in parallel with the base. The valve plates strike the stop pin and are prevented from rotating past a 90 degree vertical position with respect to the base. However, use of a diametrically extending stop pin requires either that the check valve incorporate an annular housing into which the pin is installed or that the stop pin be separately installed into the tube. Use of an annular housing adds to the complexity and expense of the valve and adds additional bulk which impedes fluid flow in the desired direction. Separate installation of the stop pin makes installation of the check valve more complex and requires that additional holes be made in the tube for the stop pin, which can create fluid leaks.
Accordingly, it is an object of the present invention to provide a fluid-actuated dual plate check valve wherein stretching of the elastomer hinge is substantially prevented.
It is a further object of the present invention to provide a dual plate check valve wherein displacement of both valve plates to one side of the valve is prevented without requiring the use of an annular housing for the valve or a separately installed stop pin.
It is a further object of the present invention to provide a fluid actuated dual plate check valve which can be used as a single point hookup for a temperature control device to heat or cool an automotive cooling system or other open or closed loop system.
Other objects and advantages of the current invention will become apparent when the inventive check valve is considered in conjunction with the accompanying drawings, specification and claims.